JEE Main 2022 · 24 Jun · Shift 1 · Physics Q41

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PhysicsSingle correct+4 / -1Question 41 of 90

A resistance of $40\ \Omega$ is connected to a source of alternating current rated 220 V, 50 Hz. Find the time taken by the current to change from its maximum value to the rms value :

2.5 ms

1.25 ms

2.5 s

0.25 s

Answer and worked solution

Official answer: A

Phase change. Take $i=i_0\sin\omega t$ . The maximum is at $\omega t=\frac\pi2$ and the next rms value $i_0/\sqrt2$ is at $\omega t=\frac{3\pi}4$ , a phase change of $\frac\pi4$ .

Time. $\Delta t=\dfrac{T}8=\dfrac{1}{8\times50}$ s $=2.5$ ms.

(A)

Topics:AC basics and RMS values

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JEE Main 2022 · 24 Jun · Shift 1, Physics question 41